UTF-8 Byte Size Calculator
Calculate the UTF-8 encoded byte size of text with mixed character ranges.
About UTF-8 Byte Size Calculator
UTF-8 is variable width, so byte length and character count differ for any non-ASCII text. Latin accented letters take two bytes, most Asian scripts three, and emoji four. Assuming one byte per character is the most common cause of truncated text and off-by-one buffer errors in internationalised software.
Formula
UTF-8 Byte Size
Bytes = ASCII + 2 × two-byte + 3 × three-byte + 4 × four-byte characters
- variable width
- UTF-8 uses one to four bytes per character depending on the code point
Worked example
With the default values below, UTF-8 Byte Size Calculator returns Total UTF-8 Size of 1,300. Change any input above and every figure here is recalculated in your browser.
Inputs used
- ASCII charactersminimum 0
- 800
- Two-byte charactersminimum 0
- 120
- Three-byte charactersminimum 0
- 60
- Four-byte characters such as emojiminimum 0
- 20
Results
- Total UTF-8 Size
- 1,300 bytes
- Total Characters
- 1,000
- Total Size
- 1.2695 KB
- Average Bytes per Character
- 1.3000
- Overhead Against Pure ASCII
- 30.00%
Step by step
- 1Values used
- 2UTF-8 Byte Size
- 3Total UTF-8 Size= 1,300 bytes
- 4Total Characters= 1,000
- 5Total Size= 1.2695 KB
- 6Average Bytes per Character= 1.3000
- 7Overhead Against Pure ASCII= 30.00
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is UTF-8 Byte Size calculated?
Bytes = ASCII + 2 × two-byte + 3 × three-byte + 4 × four-byte characters UTF-8 is variable width, so byte length and character count differ for any non-ASCII text. Latin accented letters take two bytes, most Asian scripts three, and emoji four.
Why does UTF-8 Byte Size matter?
Assuming one byte per character is the most common cause of truncated text and off-by-one buffer errors in internationalised software.
What values do I need to enter?
This calculator takes 4 inputs: ASCII characters, Two-byte characters, Three-byte characters, Four-byte characters such as emoji. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.